The present invention relates to an illumination system which images the arc of a light source into the input aperture of a non-imaging reflector, and more particularly to an illumination system for use in projection displays having a light valve in the form of a liquid crystal display illuminated by light emitted from the output aperture of the non-imaging reflector.
U.S. patent application Ser. No. 137,049, and a continuation-in-part thereof filed Dec. 9, 1988, which are hereby incorporated by reference, disclose an illumination system including a light source and a first concave mirror positioned to collect substantially all the luminous flux. emitted by the light source within a first half space and to reflect it toward a second opposite half space. The system further includes a non-imaging reflective collector having an input aperture positioned to receive substantially all of the light emitted by the light source in the second half space as well as substantially all the light reflected by the first concave mirror into the second half space.
The first concave mirror disclosed in application Ser. No. 137,049 is contiguous with the input aperture of the non-imaging reflective collector and reflects the luminous flux from the light source directly into the input aperture of the collector. Since the size of the modulation device is fixed and it is desired to keep the emission angle of the beam exiting the output aperture of the collector to a minimum, the input aperture will generally be relatively small. For example, for maximum emission angles .theta.x, .theta.y of .+-.15 degrees in air, and a rectangular light valve with a 4:3 aspect ratio and a diagonal of 48 mm, the input aperture must have a diagonal of 12 mm. This calculation is more fully discussed in Ser. No. 137,049 and the continuation-in-part thereof.